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L816-AM Hardware User Manual
Page 29 of 42
The principles for N.O. SIM card slot design are described as follows:
When the SIM card is detached, it connects an open circuit between CD and SW pins, and drives the
SIM1_CD pin low.
When the SIM card is inserted, it connects the short circuit between CD and SW pins, and drives the
SIM1_CD pin high.
Suggested SIM1_CD pin increase TVS to protect the pin.
3.5.3 USIM Hot-Plugging
The L816-AM module supports the SIM card hot-plugging detection function, which determines whether
the SIM card is inserted or detached by detecting the SIM1_CD pin state of the SIM card slot.
The SIM card hot-plugging detection function can be configured by “AT+MSMPD” command, and the
description for AT command is as follows:
AT Command Hot-plugging Detection
Function Description
AT+MSMPD=1 Enable
Default value, the SIM card hot-plugging detection
function is enabled.
The module can detect whether the SIM card is inserted
or not through the SIM1_CD pin state.
AT+MSMPD=0 Disable
The SIM card hot-plugging detection function is disabled.
The module reads the SIM card when starting up, and the
SIM1_CD status will not be detected.
After the SIM card hot-plugging detection function is enabled, the module detects that the SIM card is
inserted when the SIM1_CD pin is high, then executes the initialization program and finish the network
registration after reading the SIM card information. When the SIM1_CD pin is low, the module determines
that the SIM card is detached and does not read the SIM card.
Note:
By default, SIM1_CD is active-high, which can be switched to active-low by the AT command.
Please refer to the AT Commands Manual for the AT command.
